The invention relates to a continuous electroforming process to form a strip for battery electrodes, comprising the steps of providing a mandrel having on its surface a reusable pattern subdivided into conductive and non-conductive areas; moving said mandrel through an electroforming bath to deposit a metal layer on said mandrel while it moves through the electroforming bath until the metal layer has assumed the shape of the conductive pattern and a thickness at least sufficient to provide strength for the layer to be removed from said mandrel; and separating said layer from said mandrel. The invention further relates to a mandrel to be used in the electroforming process. The present invention is concerned specifically with the continuous production of electrodes, preferentially in foil and grid form, by electroforming, and with obtaining products of specified optimal properties.
DE 44 04 817 C1 describes a process to manufacture battery grids by electroforming. However, the discontinuous process claimed there is limited to a production of individual grids on a plate-shaped cathode. Such a process is difficult to control and is not sufficiently economical. Furthermore, modern technology of battery plate production has changed over to a continuous process. It requires that the electrodes are provided in the form of an “endless” strip-shaped feed material of electrodes connected to each other. Any new process which is to provide competitive or superior productivity and product properties will have to satisfy the requirements of the continuous plate making process.
Electrodeposition processes to produce metal continuously as a strip in sheet or foil form have been known for a long time.
U.S. Pat. No. 1,567,079 discloses a continuous electrolytic process of forming sheet cathodes comprising the initial formation of a single sheet cathode on a horizontally moving, vertically disposed surface in a winding direction, then parting the cathode from the moving surface in an unwinding direction without interrupting the electrodeposition, then interrupting the deposition and then continuing the deposition upon the initially formed cathode, as it is moved horizontally in a vertical plane, whereby a plurality of sheet cathodes will be formed upon the surface of the cathode initially formed.
DE 585 633 uses a horizontal cylinder in a similar process.
DE 197 38 513 C1 relates to a process for producing a metal foil consisting of plural metals where different electrolyte baths are used.
U.S. Pat. No. 4,169,018 discloses a process for electroforming thin copper foil on aluminum carrier material for use in printed circuits wherein a continuous strip of aluminum material is prepared by etching and rinsing steps, whereupon the prepared carrier material is passed through a single preselected composition copper plating bath having nitrate ions in the concentration of between 3 and 30 grams/liter and fluoride ions in the concentration of between 0.05 and 10 grams/liter. This bath is operated at a constant, predetermined cathode current density of between about 5.5 and 33 A/dm2 (50 and 300 A/foot2).
U.S. Pat. No. 5,236,572 which has been used to formulate the preamble part of patent claim 1 discloses a method for continuously manufacturing parts requiring precision micro-fabrication. A surface of a mandrel having a reusable pattern thereon is moved through an electroforming bath. While the mandrel surface moves through the bath, a metal layer is deposited on the mandrel surface to define a pattern. After the metal layer has been deposited to the selected thickness, the metal layer is separated from the mandrel surface.